1. Field of the Invention
The present invention generally relates to a system for sensing and informing about the water content absorbed by a disposable diaper. In its particular aspects, the present invention relates to a water content sensing and informing system for a disposable diaper which provides convenience and comfort to the person who wears it, such as babies or bedridden and aged people. Another person can easily learn of the wet condition of the diaper and change it instantly without delay.
2. Description of the Prior Art
Recently, the number of aged people has been increasing owing to the progress of medical science. The number of bedridden people has tended to increase simultaneously. In nursing hospitals for such aged people, it is estimated that at leased 30 percent of the patients are bedridden. The treatment of excrement has been a serious problem for those caring for these patients. It is obvious that providing easy treatment, for at least urine, would lighten the distress and burden of the patients and the nursing personnel.
Conventionally, two methods have been commonly used for such urine treatment. One method involves a diaper treatment using a diaper or napkin to absorb the excreted urine. The other method involves continuous urine excretion treatment using a urethral catheter, such as a balloon catheter, which must always be connected to the patient.
The above mentioned diaper treatment will be discussed in detail as the present invention is related to that type of treatment. In hospitals or nursing homes, the changing of the diapers of the patients is fixed at certain intervals because the nurse has no way of knowing whether all of the patients have urinated. However, with this method, some of the patients may be left with a wet diaper for a long time, thereby causing discomfort and pain due to diaper rash, cooling, bed sores and the like.
In order to learn of the urination of such patients, a particular method of detecting the water content, as in urine, has been provided. The method of detecting the water content by means of changes in the electric conductivity of electrodes, such as of an electric wire installed in the diaper, is known. With this method, the urination can be detected, but it does not permit a determination of the degree of wetness of the diaper. Therefore, a water content sensing system for disposable diapers has been proposed in our prior invention (Japanese Patent Application for Utility Model No. 59-71558) which system is illustrated in FIG. 8 and FIG. 9.
In the prior art illustrations, FIGS. 8 and 9, a disposable diaper equipped with a water content sensing means is shown. The diaper comprises a water permeable inner sheet 1, a water absorber 2 and a water impermeable outer sheet 3. Further, both side ends 3a of the outer sheet 3 are bent over to cover the periphery of the absorber 2. Each bent section is pinched between a pair of metal layers 4, as shown in FIG. 9. Each metal layer 4 is connected to a lead wire 5. Because of this construction, the absorber 2 is pinched between the outer sheet 3 and the pair of metal layers 4 and thereby a capacitor is formed. The electrostatic capacity of this capacitor corresponds to the amount of the water absorbed by the absorber 2. The degree of wetness can be determined by monitoring the changes in the electrostatic capacity through the use of a well-known measuring device which is connected to the lead wires 5.
This capacitor-type water content sensing diaper provides comfort to the patients, as wet diapers can be changed by the nurse or nursing person who learns of the degree of wetness of the diaper through the detecting device. However, the capacitor formed by this type of structure frequently causes erroneous detection of the degree of wetness due to the deformation of the metal layers 4. The distance between the two metal layers 4 can be changed by their becoming broken, disconnected or twisted. This can result in the erroneous measurement of the electrostatic capacity because the electrostatic capacity is proportional to the area of the metal layers and the dielectric constant of the water absorber 2 and is inversely proportional to the distance between the two metal layers. The deformation of the metal layers 4 can easily occur due to the movement of the patients or babies or whoever is wearing the diaper. Erroneous measurement of degree of the wetness may be caused by fluctuations in the electrostatic capacity, as described above.
The detecting and informing device is connected to each diaper, so that a nurse or a nursing person has to go look at each informing device to determine the wetness of the patient's diaper.
3. Objects of the Invention
It is an object of the present invention to provide a water content sensing and informing system for a disposable diaper which can detect the degree of wetness of the disposable diaper without requiring checking by a nursing person.
Another object of the present invention is to provide a water content sensing and informing system for a disposable diaper which can transmit the detected information to a remote location.